Secondly every Huffman tree must have following structure code, data, weight, parent, l-child and r-child but only code and data are needed in decoding .

而且每棵哈夫曼树都必须有以下结构：编码，信息，频度，双亲，左孩子，右孩子。

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Chained data structure keep hit-set by its L-length. it does not need to create ancestor nodes, so it can reduce the saving of none hit-set and the room of matching the patterns.

层状链式图是根据模式的L长度分层存储命中模式，它不需要按照直接可达祖先思想创建路径的节点，因此减少了非命中模式节点的存储。

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